Excursion to Cornwall: Monday, August 8th, to Saturday, August 13th, 1887

196

EXCURSION TO CORNWALL.

MONDAY, AUGUST 8TH, TO SATURDAY, AUGUST 13TH, 1887.

Directors: THE PRESIDENT; WILLIAM THOMAS, F.G.S., Secretaryto the Mining Association and Institute of Cornwall; andA. K. BARNETT, F.G.S., of Penzunce.

(Report by THE P~ESIDENT.)

As this was the first occasion on which a visit of tIle Associationto the West of England had been extended beyond the TaIllar, anunusual1y large number of Members and friends availed themselvesof the advantages afforded by the Excursion. Most of the partytravelled from London to Truro on Saturday, August 6th, andthese had not struck far into Cornwall before an interesting rockpresented itself for examination. An opportune halt for half anhour at Menheniot Station enabled the party to leave the trainand examine the well-known serpentinous rock to which theirattention had been directed by Mr. W. Semmons. A quarry ofthis rock close to the station afforded specimens of what is sometimes known as the "Clicker Tor Serpentine "-3 rock which hasbeen described by Mr. J. A. Phillips,'*' Mr. S. Allport,t Mr.Collins,t Mr. Teall,§ and Prof. Rosenbusch.1I It is regarded byMr. Allport as an intrusive mass of olivine-dolerite partially converted into serpentine, while Prof. Rosenbusch considers that theoriginal rock was a picrite. Its microscopic structure is wellfigured by Mr. Teall, who describes its character as that of analtered" ophitic dolerite (diabase), in which oliville was present ingreat abundance and felspar only to a very small extent."-' Brit.Pet.; PI. II., Fig. 2.

.Monday.-The real work of the week commenced early onMonday morning, wIlen the party assembled at the Royal Institution of Cornwall, ill Pydar Street, Truro. Here they werecordially received by Mr. Nicholas Whitley, F.G.S., Vice-President,:l\1ajor E. Parkyn, Hon. Sec., Mr. H. Thomas, Mr. Howard Fox,

* , Phil. Mag.,' xli, 1871, p. 100.t 'Quart. Journ. GeoJ. Soc.,' xxxii, 1876, p. 422.t 'Geol. Mag.,' Dec. 3, Vol. iii, 1886, p. 364.§ , British Petrography,' 1886, p. 124.\I • Mi\;:. Pbys.,' Bd. ii, 1877, p. 530.

EXCURSION TO CORNWALL. 197

and several other representntive members of the Institution. Theformal reception took place in the lecture room, where Mr.Whitley occupied the chair. After welcoming the party, theChairman gave a general sketch of the geology of Cornwall, andcalled attention to the distribution of flint flakes and shatteredflints in the county. Major Parkyn supported the Chairman inextending a welcome to the Association. Mr. Howard Fox thendescribed the serpentine and associated rocks of the Lizard distl'ict,of which he had brought a fine display of specimens for exhibition to the meeting. The courteous reception having been dulyacknowledged by the President, who also expressed his appreciation of the instructive addresses which had been delivered, theparty visited the Museum under the guidance of the representativesof the Institution previously named.

Those of the party who cultivated a taste for mineralogy manifested keen interest in the collection of minerals. This collectionhad been arranged and catalogued some time back by Mr. J. H.Collins, F.G.S. Among Cornish minerals special note should bemade of the :line specimens of native gold from the Carnon steamworks, the native silver from Fowey Consols, and the nativecopper from the Lizard and other localities in the west. Theseries of Cornish cassiterites, including such forms as "sparabletin" and "robin tin," is at once fine and extensive. The Cornish fossils collected by the late Mr. C. W. Peach also attracteddue attention. But the glory of the Museum lies in its antiquarian treasures. Here is to be seen the unique ingot of ancienttin, dredged up about sixty years ago near St. Mawes, at theentrance to Falmouth Harbour, and supposed to be one of the"astragali" mentioned by Diodorus Siculus. The late Sir HenryJames explained the shape and size of this peculiar block as beingspecially convenient for transport in boats from Iktis to Gaul, andthence on horseback overland to Marseilles.'" Here, too, is thelittle bronze image of a bull found in St. Just, and regarded as arelic of Phcenician intercourse.t But perhaps the most generallyinteresting objects in this department are the two gold lunulce orpenannular ornaments found in 1863 at Harlyn, near Padstow.The cinerary urns unearthed from various tumnli, the implements

• • Note on the Block of Tin dredged up in Falmouth Harbour,' byCol. Sir Heury James, R.E. Stanford: 1863.

t Fignred in Robert Hunt's 'British Mining,' 1884, Fig. 2, p. 15.

198 EXCURSION TO CORNWALL.

in stone and bronze, with the stone moulds for casting bronze celtlJ,and the blocks of" Jews' tin" or masses of metal from the ancient" blowing houses" of Cornwall, were among the many local objectswhich gave special interest to the visit to the Truro Museum.

FIG. 1. Map of the country north of St. Austell visited on Monday,August 8. Scale, half an inch to one mile. The HensbarrowGranite is dotted; the schorl-rock of Roche is indicated byvertical shading; and the Killas left blank.

On leaving Truro by rail for St. Austell the party was joinedby Mr. J. J. Beringer, F.C.S., Lecturer to the Mining Association and Institute of Cornwall, who had come from Camborne toassist in conducting the Excursion. On reaching St. Austell theMembers were received by Mr. R. H. Williams, F.G.S., underwhose guidance they proceeded in conveyances to Carclaze mine,anout two miles north of St. Austell. Here, in the midst of abroad expanse of waste land, commanding an extensive andpicturesque view, the visitors found themselves in the presence ofa vast open excavation, about a mile in circuit. Worked at thepresent time chiefly for China-clay, this pit was originally openedas a tin mine, 'the decomposed granite, or "soft growan," beingtraversed by veins of cassiterite, or tin-stone, associated withschor! or black tourmaline. Mr. Williams sketched the history ofthe mine and deticribed tlw present method of working. It is

EXOURSION TO CORNWALL. 199

probably the oldest excavation in Cornwall, its history stretchingback for five centuries. According to the late Mr. R. Symons itoccupies an area of 13 acres, and reaches a depth of 132 feet.""

..;v. S.

FIG. 2. Section of Carclaze Old Pit. (J. H. Collins.) Visited on Monday,August 8.

A. Rather hard Granite, with thin schor! veins, some dippingsouth, and others vertical.

B. China.clay rock, or Carclazite, with schor! veins, and veinsof Quartz aud Greisen.

C. Tourmaline schist, gradually passing into D.D. Reddish and brownish Killas, or Clay-slate.E. Overburden, containing and capped by loose boulders.

From Carclaze the party proceeded to Minear Downs, an openwork, where branches of tin-ore are seen traversing the Kinasor clay-slate. Having returned thanks to Mr. Williams for hiscourteous assistance, and to Messrs. John Lovering and Co. forpermission to visit the pits at Carclaze an,i Minear Downs, theparty returned to St. Austell, and after being refreshed by luncheonstarted in conveyances to the extensive workings of the West ofEngland China-clay Company, near Nanpean. Here they weremet by Mr. Stocker, jun., who conducted the party over the worksand explained in detail the several operations of preparing the clay.In formally thanking the proprietors and those who had renderedtheir services on this occasion, the President, responding to thewishes of the party, entered at some length into the subject of thenature and origin of China-clay and China-stone

The discovery of China-clay, or Kaolin, in England dates fromabout the year 1750, when William Cookworthy, of Plymouth,having seen certain samples of the clay and of the china-stone, which

* For recent descriptions of Carclaze pit see 'The Hensbarrow GraniteDistrict,' by J. H. Collins. Trnro: 1878, p. 36. Also' Geology of Cornwall,' by Brenton Symons. Londou: 1884, p. 140; and a paper "OnCarclazc Tin and China.clay Pit," by R. Symons, in 'Journ. R. lnst. Cornwall,' Vol. vi, 1881, p. 140.


had been brought from America, found similar materials at Tregonning Hill, in the West of Cornwall, and at St. Stephen's, in theHensbarrow district. The ChinEse names by which these substancescame to be known-Kaolin and petuntze-were due to the Pered'Entrecolles, a French Jesuit, settled in China, who sent toReaumur, in Paris, 'samples of the materials used by the Chinesein their porcelain manufacture. It appears, however, that his namesare not those generally applied to similar suhstances in China.'*'Cookworthy, using the local phraseology, called the petuntze orChina-stone "growan" or "moor-stone," while the Kaolin hedescribed as "growan clay." With these materials he madeexperiments on the production of hard-paste porcelain at Plymouth,t and songht to establish its manufacture at Bristol.

The China-stone is a granitic rock, composed generally of quartz,white felspar (partially decomposed), and gilbertite. This rockMr. Collins distinguishes as Petuntzite. The rock from whichChina-clay is prepared iB a granite in a much more advanced stateof alteration, the felspar having been converted into kaolin, orpure clay: it consistB of quartz, kaolin, and mica; the Cornishrock generally containing two micas. As the China-clay rock iswell seen in the "Boft growan" of Carclaze, Mr. CollinB hastermed it Carclayzite. The method of washing the clay from therock is described· in his paper recently read before the Association(vide supra, p. 111).t

It will thus be seen that the essential difference between thecarclayzite and the petnntzite lies in the fact that in the former thefelspar has not been completely kaolinized, and therefore stillretains some of its alkaline silicate, which confers fusibility uponthe rock, while the Kaolin itself is practically infusible. It isconsequently to the China-stone that porcelain owes its translucency; it is this that forms what the Chinese call the "flesh" ofthe ware, while the clay constitutes its "bone." Specimens ofChina-stone, fused to a vitrified mass, were distributed to the partyas an illuBtration of the properties and use of thiB material.

* See' Histoire et Fabrication de la PorceJaine Chinoise,' by M. StanislasJulien. Faris, 1856.

t .. William Cookworthyand the Plymouth China Factory," by R. N.Worth, F.G.S., 'Tran$. Devon A$soc.,'Vol. viii, 1876, p. 480.

t See also Mr. Collins's 'Hensbarrow Granite,' which contains detailedinformation and bibliographical references respecting China-clay and stone(pp.W to 36).

EXCURSION TO COI\NWALL. 201

The alteration of the granite is popularly attributed to theaction of carbonic acid in meteoric waters, but there are considerable difficulties in accepting so simple an explanation, and thosewho have given most attention to the subject are inclined to believe,as maintained by M. Daubn\e, that hydrofluJric acid, or otherfluorides, must have been the chief agent in attacking the felspar.*The presence of compounds containing fluorine, such as tourmaline,lepidolite, and fluor-spar, is very common in China-clay districts.Fine examples of fluor-spar, presenting a deep amethystine tint,were found by the party when examining the China-stone quarriedat the West of England works.

In compliment to the Association, the Royal Institution ofCornwall had kindly organized an evening conversazione, at whichthe members of the two bodies had an opportunity of becomingacquainted with each other. The geologists were very courteouslyreceived by the Rev. W. Iago, M.A., the President; Mr. H. M.Jeffery, F.R.S., Vice-President; Major Parkyn, Hon. Sec., and alarge party of members. After tea and coffee had been served, theparty adjourned to the lecture room, where the President of theInstitution took the chair, and offered a formal welcome to theAssociation, accompanied by an invitation to join in the annualautumn excursion, which would this year be to the neighbourhoodof Bodmin. The reception and invitation were gratefully acknowledged by the President of the Association. Mr. E. A. Wunsch,F.G.S., then delivered an address, in which he expressed his viewson the nature of metamorphism, and on the origin of the Lizardserpentine. A discussion ensued, in which the Association wasrepresented by the President, Dr. Foulerton, and OolonelMcMahon.Some sections of Cornish rocks were exhibited under the microscope by Mr. Thomas Clark; and other objects of scientificinterest were brought forward by members of the Royal Institution, thus contributing to render this meeting one of the mostpleasant gatherings during the week of the Excursion.

Tuesday.-Those of the party who were not afraid of a longday's work on Tuesday paid an early visit to the Cathedral works,where they were received by Mr. Robert Swain, the Clerk of theWorks, who pointed out the different kinds of stone employed in

* See' Etudes synthetiques de Geologie exp6rimentale,' par A. Daubree.Paris, 1879, p. 29.


this structure. The following note on this subject is taken froma recent paper by Mr. R. N. Worth, F.G.S."" :-" The exteriorashlar work is of Mabe granite, the interior ashlar of St. Stephen'sstone (China-stone), a form of aplite j the body of the walls beingfilled in with local walling stone-killas, chiefly from Ideless, nearTruro. The vaulting shafts in choir and transepts, and also in thebaptistry, are principally Polyphant, with Duporth stone in someinstances, and some Duporth is also introduced in the shafting in thetriforium. The small arcade on the east wall of the south transeptwill contain a series of shafts of red porphyry from Carnsew,Stithians, given by the late Colonel Somers Cocks; and serpentine is also to be introduced. Pentewan, Wild Duck, Newnham,and other elvans were used partially by way of experiment inrestoring the lower part of old St. Mary's ornate south aisle." Inaddition to these local stones, use has been made of oolitic limestones from Bath, from Doulting, in Somersetshire, and fromNorthamptonshire; as also of "Frosterley Marble," a blackvariety of Carboniferous Limestone, rich in fine corals, from nearStanhope, in Durham. Much interest was taken in thematerial from Duporth, concerning which Sir W. W. Smyth hasremarked that it " had been brought into use in the Cathedral withgreat effect for columns and other purposes, and it might hold upits head and claim to be quite as halldsome and suitable to thepurpose as the Purbeck marble that was found in churches in otherparts of the country." t

At 9.27 the party left Truro by rail, and on arriving at CarnBrea Station were met by Mr. William Thomas, who had organizedthe arrangements for the day, and by a number of other gentlemenrepresenting the Mining Association and Institutc of Cornwall.The party was now divided-one group going with Captain C. F.Bishop to East Pool Mine, and another with Captain W. T. Whiteto Wheal Agar, while the bulk of the party ascended Cam Brea.Those who went underground were unable to rejoin the principalparty until the afternoon. The Cam Brea division-conducted byCaptain Josiah Thomas, of Dolcoath, Captain Teague, of CamBrea Mine, and .Mr. W. Thomas-having made their way to thesummit of this rugged hill of grey granite, 738 feet high, were

* "The Rocks and Minerals of Cornwall and Devon," 'Fifty.fourthAnnual Report of the R. Corn. Polytech. Soc.,' 1886, p. U.

t ' Fifty-fourth Rep. R. Corn. Polytech. Soc.,' 1886, p. 26.

~or'

xZ?"'-

....-.]

, ....

~/':IMo~'"~z~<;oJ;>;Z

~to<r'

FIG. 3. MAp of the country between lledruth and Camborne, showing the mines in the neighbourhood of Cam Brea, visited onTuesday, August 9. Scale I{; inch to 1 mile. (From MoisBenet, after Mr. R. Symons.) In this map the name of Dolcoathhas been accidentally omitted. The mine is situated a little to the East of Camborne.

~otIO

204- EXCURSION TO CORNWALL.

rewarded for the rather toilsome ascent by a magnificent viewstretching across the country from sea to sea. The principalfeatures of interest in this panorama wcre pointed out by theDirectors, who called attention to the connexion between thephysical characters of tIle country and its geological structure.Splendid examples of weathered granite were presented by thespheroidal boulders and fantastically-worn rocks on this hill; anddiscussion arose as to the formation of those rock-basins, loganstones, and other objects which the early antiquaries of Cornwallregarded as monuments of Druidical worship.

9.S.E'.

GRANITE,',

, .., . '...~.. ~ ,

FIG 4. Section of Granite and KiIlas, with Lodes, near Carn Brea;(Moissenet.) Scale, 211.0'

Before leaving the summit of Carn Brea the excursionists wereinvited by Captain Teague to partake of refreshments, which hehad thoughtfully ordered to be carried up the hill by a party ofbal maidens, an invitation which, under the mid-day sun of asultry August day, was gratefully accepted. After descending thehill, the visitors inspected the surface-workings of Carn Brea,Tincroft, Cook's Kitchen, and Dolcoath. At Cook's KitchenCaptain Charles Thomas kindly distributed some specimens of theores of the district, and at Dolcoath Captain Josiah Thomasentered into a full description of the surface-machinery, and of theoperations on the dressing floors. A substantial luncheon wasprovided at Dolcoath, and, in replying to a vote of thanks for thishospitality, Captain Josiah Thomas gave some interesting detailsrespecting this extraordinary mine. Dolcoath was started in 1799,and is now about 420 fathoms deep. The mine is something likethree-quarters of a mile in length, and out of this piece of groundthere has been already returned copper to the value of £3,500,000,and tin to the value of nearly £3,000,000. The total outlay hadbeen £40,000, and the annual profits were now about £50,000.The number of hands employed at Dolcoath is about 1,350.

The party was now reillforced by those who had spent the morning underground, and who ret.urned delighted with their Bubter-

EXOURSION TO CORNWALL. 205

ranean experiences; nor were they less warm in acknowledgingthe courtesy of Oaptains Bishop and White, who had not onlyshown them every attention below, but had provided for theirentertainment above ground. As the conditions under which theores of tin and copper occnr in Oornwall and the method of working them are well explained in Mr. Oollins's paper,'*' it is needless torefer to the subject here. Sufficient to say that the i~terest of theparty in Oornish mining was much enhanced by several valuablepapers on the subject, which had been obligingly sent by Dr. O. LeNeve Foster, F.G.S., for distribution among the party.

In the afternoon the geologists had the privilege of meetingthe members of the Mining Association and Institute of Oornwall,whose President (G. L. Basset, Esq.) had invited the two bodiesto a banquet at 'rehidy Pari" About 170 sat down in the magnificent rooms of this mansion. It unfortnnately happened thatillness prevented MI'. Basset from being present, but his placewas efficiently taken by Mr. T. Elliot Boog. After the usual loyaltoasts had been proposed and honoured, Mr. G. J. Smith gave"The Bishop, Clergy, and Ministers of all Denominations," towhich the Rev. Oanon Rogers replied. Mr. R. H. WilliaII).s thenproposed, in complimentary terms, " The Geologists' Association,"which was duly responded to by the President. Mr. T. V. Holmesnext proposed" The Mining Association and Institute of Oornwall," to which Captain Josiah Thomas returned a felicitous reply.Finnlly, Captain Henderson proposed "The Health of Mr. Basset,"which WDS suitably acknowledged by Mr. Boog.

The principal rooms of the mansion having been' visited afterluncheon, most of the Members strolled through the beautifnlgrounds until a start was made in open carriages for Hayle. Thislong ride enabled the Members to appreciate the fine scenery of theNorth Ooast of Oornwall, and halts were made from time to timein order to allow of a closer examination of the rocks. The cliffsof slaty rocks rise at some places sheer from the sea to a height of300 or 400 feet. Much interest was also taken in the hills ofblown sand at Godrevy and Gwithian. Hayle Station was reachedill time for the last train to Penzance, where the party took quartersfor the remainder of the week.

Wednesday.-At ten o'clock on Wednesday morning the geologists left Penzanee for St. Erth, where they were anxious to

lI' 'Sketch on the Geology of Cornwall and West Cornwall.' Supra, p. 101


examine the Pliocene deposits which, since their discovery in 1882,have been the subject of considerable discussion. At St. ErthStation the party was met by Mr. G. Bown Millett, Hon. Secretary of the Royal Geologicl\l Society of Oornwall, and by Mr.Fortescue W. Millett, F.G.S., of Marazion, who, having speciallystudied the St. Erth beds, had kindly consented to describe them.Later in the morning the geologists had the advantage of beingaccompanied by Miss Goodman, a lady resident at St. Erth, whohas paid great attention to the local fossils.

The following note on the Pliocene deposits of St. Erth has beenobligingly furnished by Mr. Robert W. Bell, F.G.S. :-*

"The St. Erth Pliocene beds were first noticed about five yearsago in the course of excavation for clay used for puddling thePenzance dock which was theil building. The clay may be seen inone corner of the large Sand Pit close to, and belonging to, theVicarage of St. Erth.

" The upper portion consists of that deposit which is almost universal in West Oornwall, and is known as 'Head.' It is clayey,and crammed with angular pieces of killas and other local rocks.Beneath the head is yellow sand, in one part of which could be seenlast year some evidence of the crumpling up of the bed similar tothat prevalent in some of the Glacial Deposits over the crags ofthe Eastern Oounties.

" Below this is clay, the upper part yellow without fossils, and thelower blue with shells, getting more numerous towards the base.The most numerous are Turritella, a large Nassa, and, at the lowerfossiliferous portion, numbers of small Cedtkia. The clay is alsovery rich in Foraminifera, and spicules of Holothllrians and Tunicates. About 150 species of Mollusca, mostly small, have beenobtained from careful washing of the clay.

" Below this is a bed of Quartzose Sand resting- upon Elvan."

After the Association had arranged to visit this localityit was found that the section was no longer visible, and thatit would require considerable labour to prepare a fresh exposure. This work was kindly undertaken by the RoyalGeological Society of Oornwall, who, baving with some difficultyobtained permission for the visit, went to the expense of employinglabourers to cut a new section in view of the visit of the London

* While these sheets were passing through the press the Reporter heardwith extreme regret of the death of this accomplished conchologist.

EXCURBION TO CORNWALL. 207

geologists. The visitors con sequently found themselves in thepresence of a fine, fresh exposure of the fossiliferous bedll, and themore zealous members of the party came away enriched with itsBpoils.

Vegetable Soil.~""&."-5.- Head.

r Yellow Sand.

I]" Growder."

t~~Yellow Clay.Blue Clay with Fossils.

~.v-~~ Quartz Pebbles.I'il

.... "

0 Fine Quartzose Sand.0H...Il;

.....-.' " "Growder."L :::. ;,:. ' ..;;,~.,~~.<~'>~:;

Elvan Dyke.. "')- .... 1' I •

. .". . ~ .."'".,....,.. t

FIG. 5. Section at St. Erth, 1885. (Kendall and Bell.)

Mr. Fortescue Millett, in describing the fossils of St. Erth,dwelt especially upon the foraminifera, since it is these to which hehas given special attention. He has recognized no fewer than 120distinct forms, of which five ar e extinct and 115 now living invarious seas. The extinct species are Lagena margino-mdiata,Globigerina cretacea, Rotalia punctato-granosa, Faujasina carinata,and F.orbignyi. Of the living species 92 are found in the Britishseas. The following nine forms are here found fossil for the firsttime, namely :-Bolivina j'obusfa, B. to,'tuosa, Cassidulina bradyi,Discorbina patellcefo1'lnis, D. wrightii, Truncatulina' tenuimm'ga,Rotalia dentata, Polymorphina concava, and Spirillina limbata,val'. decorata. It is noteworthy that Textularia quadrilatem,which occurs here, has been found fossil in the Pliocene deposits ofKar Nicobar, and is now living in the Canaries and Cape de VerdeIslands, but occurs most abundantly in the South Pacific.*

From St. Erth the party returned by rail to l\larazion, wherethey were met by Sir W. W. Smyth, F.R.S., the President of theRoyal Geological Society of Cornwall. Sir Warington and LadySmyth hospitably entertained the excursionists at their countryresidence overlooking Mount's Bay, and in the afternoon accompanied them to St. Michael's Mount. After pointing out by theway such features as were of special interest to geologists, Sir

" .. Additional Notes on the Foraminifera of the St. Erth Clay," byFortescne William Millett; 'Trans. R. Geol. Soc. Cornwall,' 1886.


Warington selected a suitable position on the southern side of themountain base, where he delivered an admirable address on thegeological and mineralogical characteristics of the Mount.

The lecturer first called attention to the junction of the granitewith the killas, and to the metamorphism which the latter hadsuffered by this contact. Both the grauite and the killas wereintersected by a system of veins, well displayed at the spot wherethe party had assembled. Some of these veins were of granite,which, when in a condition of greater or less fluidity, had beeninjected into cracks in the slaty rocks, and these veins had beenthe subject of discussion as far back as the time of Sir H. Davyand Dr. Boase. In addition, however, to these granitic veins therocks presented a series of mineral veins, some of which, beingstanniferous, were veritable tin-lodes in miniature. These veinspresented a very noteworthy parallelism, cropping out in east andwest lines, two or three feet apart, with almost- mathematicalregularity. The granite in the immediate neighbourhood of the veinshas been converted into a granular rock, consisting chefly of quartzand mica, and strongly resembling the Greisen of the tin-miners inSaxony. Quartz was the most common constituent of the veins onSt. Michael"s Mount, but associated with the quartz were a numherof fluorine-bearing minerals of much scientific interest. One ofthese was lepidolite, or lithia-mica-a mineral which occurscharacteristically in the tin-lodes of Altenberg, in Saxony, andZinnwald, in Bohemia. Sir Warington dwelt upon the similarityof conditions under which tin-ore occurs at St. Michael's Mount,and in the mines of the Erzgebirge, between Bohemia and Saxony.The resemblance is supported by the occurrence of topaz at theMount, a mineral which contains as much as 17 per cent. offluorine, and which also occurs in Saxony, especially in the wellknown topaz-rock of the Schneckenstein, and in the columnarvariety found at Altenberg, and distinguished as pycnite. Thetopaz now found at St. Michael's Mount is in the f0rm of colourless crystals, so small as to be recognized only with difficulty.Beryl likewise occurs, as also apatite, fluor-spar, and tourmaline.Of metanic minerals he noted the abundance of wolfram, associatedin places with wolfram ochre; while there were also presentmispickel, or arsenical pyrites, copper-pyrites, and, ahove an else,cas~iterite or tin-stone. Sir W. W. Smyth pointed out the similarassociation of many of thesc minerals with tin-ores in other parts ofthe world, and referred to M. Daubree's ingenious explanation of

EXCURSION TO CORNWA.LL. 209

such paragenetic relations by assuming that the group of mineralshad been deposited by the decomposition of various fluoridesuerived from deep-seated sources in the earth's interior. Crystallized oxide of tin is obtained by passing a current of stannicchloride (or fluoride?) with steam through a red-hot tube. Thereaction of the fluorides on the granite would probably give rise tomost of the common associates of tin-ore as suggested by the experiments in which Daubn\e produced artificial apatite and topaz.'*'

After Sir W. W. Smyth had concluded his instructive discoursehe conducted the party to the best spots for observing thephenomena which he had been describing. Later in the day mostof the Members visited Lord St. Leven's Castle, picturesquelyseated on the summit of the Mount, and thus forming the apex ofthis great pyramidal boss of granite. After bidding a gratefulfarewell to Sir Warington and Lady Smyth the excursionistsreturned to Penzance.

Thursday.-At nine o'clock on Thursday morning the party assembled at the Museum of the Royal Geological Society of Corn.wall, where they were received by Mr G. Bown Millett, Hon. Sec.,Mr. A. K. Barnett, F.G.S., Hon. Curator (who acted as conductorthroughout Thursday and Friday), and Mr. Ambrose Taylor,Assistant Curator. These gentlemen, accompanied later on by Mr.Thomas Cornish, were unsparing in their attention to the visitors.The ground-floor of the Museum is devoted to the colIection offossils, which was arranged in 1878 by Mr. Etheridge, F.R.S., andincludes a fine series of Silurian and Devonian fossils from Cornwall, collected chicfly by the late Mr. C. W. Peach. The extensive mineral collection is located on the upper floor, and is arrangedon the principle adopted in the Museum of Practical Geology.Here the visitors had an opportunity of inspecting to great advantage the minerals of the county, including the rarer species, as alsoa collection of local rocks. The educational value of the Museum isgreatly enhanced by the system of clearly labelling the specimensand by the publication of an excelIent guide-book. t

* For Daubree's collected papers on this subject see his 'EtudessyntMtiques de Geologie experimentale,' 1879. See also Sir W. W. Smyth's"Remarks ou the Geology of St. Michael's Mount," in 'Trans. Min. Assoc.and lust. of Cornwall,' Vol. i, 1887, Part iii, p. 132; and Dr. C. Le NeveFoster's" Remarks upon the Tin-Deposits of East Wheal Lovell," in • Trans.H. Geol. Soc. Cornwall,' Vol. ix, 1876, Part ii.

t • Guide to tbe Museum of the R. Geol. Soc. of Cornwall, Pcuzance,' byO. Le Neve Foster, B.A., D.Se" F.G.S., lIud A. K. Barnett, F.G.S. 1880. l:>vo.,pp. 15. Priee one penny.


Before leaving the Museum the President of the Associationtook occasion to thank the Society not only for the privilege ofinspecting the Collections, but for the great aid which it hadrendered to his party in connexion with the St. Erth pit. Hereminded those present of the excellent work which had beenaccomplished by the Society since its formation in 1811, as attestedby its publications, including the valuable treatises of the late Mr.W. J. Henwood; and while recalling the past he heartily wishedthe Society an equal measure of prosperity in the future.

Tl)L PEDE"PEM""tTH

QRAN'TE [·.:·.·.1 ·CRE.E.NSTONe::S"~

Elvan4' • Lorks &tros$"~~FIG. 6. Map of the Western extremity of Cornwall, including the districts

visited on Wednesday, Thursday, and Friday, August 10th, 11th, and12th. Scale, 1 inch to 4 miles.

The excursionists then took carriages for St. Buryan, wherethey visited the church (temp Hen. VII.) and the ancient stonecrosses. Thence they drove to Treryn, and after luncheon walkeddown to the cliffs, in the neighbourhood of the Logan Rock. In


this magnificent headland they had an opportunity of studying thebehaviour of granite when exposed to marine action and to subaerial denudation. Meteoric agencies operating along the jointsof the granite had first divided it into cuboidal masses, and then,rounding these blocks, had produced the phenomena of rocking orlogan stones. The ease with which the great stone, weighing upwards of 60 tons, can be made to rock was practically illustrated bythe more adventurous spirits of the party, who climbed to the verysummit of the pile of rocks and set thtl ponderous mass in oscillation. A brief description of the rock was given by Mr. Barnett.

After walking for some distance along the cliffs, a descent wasmade to the beach at Porthgwarra to inspect an interestingpassage worn in the picturesque rocks, to which attention had beencalled by Mr. Thomas Cornish.

Then ascending the cliffs a short walk brought the party to TotPedn Penwith, or the" Holed Headland of Penwith," a promontorywhich takes its name from the large tunnel-like chasm in thegranite opening below into the sea. From this interesting spota journey was made, partly on foot and partly in conveyances, tothe Land's End-the extreme western point of England-whencethe party drove back to Penzance.

The object of the day's excursion had been to acquire familiaritywith the peculiarities of granite scenery-both inland and along thecoast-scenery which, to many of the party, presented much novelty.

Friday.-Early on Friday morning the party visited Messrs.Bolitho's smelting works at Chyandour, permission having beencourteously granted by the proprietors. In consequence of afamily bereavement, Mr. T. S. Bolitho was unable to be present,but in his absence every attention was paid to the visitors by Mr.A. K. Barnett, the manager, who conducted the party through theworks and explained the successive stages in the operations ofsmelting and refining tin. A charge of dressed ore, or "black tin,"mixed with culm, is thrown into a reverberatory furnace, and, fromtime to time, well stirred with a rabble; in about six hours from thetime of charging, the furnace is tapped, and the metal, or "whitetin," is run out, accompanied by slag. The charging of one furnaceand the tapping of another were witnessed. The operation ofrefining this crude tin is effected 011 the hearth of a reverberatoryfurnace, where the blocks are subjected to liquation. The morefusible tin is run out into a huge cast iron ,. kettle," in which the

212 EXCURSION 'ro CORNWALL.

metal, kept hot by a fire beneath, is subjected to " poling." Thisprocess caused much amusement. A large billet of green applewood, held by a crutch, was introduced into the molten tin, whichimmediately commenced to " boil," the tin being splashed about inall directions. The dross was then skimmed off and the refinedmetal ultimately ladled into moulds, where it consolidated intoingots, bearing the brand of the works. Pieces of tin stampedwith the well-known "lamb and flag" of Chyandour were broughtaway as interesting souvenirs of this very instructive visit.

At the gates of the tin-works carriages were waiting to conveythe party to Carne, whither they had been invited by Charles C.Ross, Esq. The object of this visit was to inspect the ma,gnificentcollectiou of minerals in Mr. Ross's private museum. This building contains the historical collection of Cornish minerals, originallyformed by Mr. Joseph Carne, and augmented by the late MissElizabeth Carne, to whom the arrangement of the mineral collection in the Penzance Museum is also largely due. Importantadditions to the Carne Museum llave likewise been made fromtime to time by judicious purchases by its present owner. Thevisitors were most cordially received at Carne by Mr. and Mrs.Ross, and after admiring the beautiful grounds and partakingof refreshments, which had been generously provided, they proceeded to the inspection of the Museum. Here the mineralogists were particularly interested in the fine specimens ofminerals obtained many years ago from St. Michael's Mount, andfrom various Cornish mines long since abandoned, including manyspecimens of surpassing beauty and extreme rarity. Nor had themore recent discoveries in Cornwall been neglected, as witnessed.for instance, by the fine Henwoodite from West Phrenix Mine,and the magnificent Diallogites from St. Just. The party, beforeleaving, expressed their sincere pleasure at this visit and theirgrateful acknowledgment of Mr. and Mrs. Ross's hospitality.

From Carne a long drive westwards, over a plateau of greygranite, presenting some wild moorland scenery, brougLt the partyto the little mining town of St. Just. A short walk thence led tothe fine cliffs of Cape Cornwall, where some interesting examplesof contact-metamorphism were studied. Under the guidance ofMr. Barnett, accompanied by Mr. W. Thomas, Mr. Herbert W.Smyth, and others familiar with the locality, the excursionists madetheir way along the cliffs to the surface-workings of the famoussubmarine mines of Botallack and Levant. At Levant they were


received by Captain White, who explained the mmmg machinery,including the "man-engine," or apparatus for the descent andascent of miners. By his permission, too, they overhauled theparcels of ore upon the floor of the mine, and thus secured specimens not only of the ordinary yellow copper-ore, or chalcopyritesome of which was brilliantly iridescent, forming the attractive" peacock-ore "-but also of the rarer ores---{)opper-glance, orredruthite, and" horse-f1esll ore," or erubescite.

A descent was then made towards the shore in order to gaina better view of the magnificent cliffs which are traversed bythe outcropping copper and tin-lodes. These veins not onlyseam the exposed rocks, but pass thence under the Atlantic,whither the adventurous miner has followed them for a considerable distance. The hornblende-rocks in this neighbourhood arenotable for containing a store of interesting minerals, such asaxinite, garnet, and epidote; but failing to secure these raritiesthe geologists had to remain content with having seen representative specimens in some of the museums which they had visited inthe county. From Levant they walked towards St. Just, andthence drove home to Penzance.

Satul'day.-An eadynecessary by the longdistrict of the Lizard.

start on Saturday morning was rendereddrive which had been arranged to theAt Helston a short halt was made. In

FIG. 7. Map of the Lizard District, visited on Saturday, August 13th.Scale, 1 inch to 1 mile.

214 EXCURSION TO OORNWALL.

due course the wild downs of the Lizard district were approached,the beautiful little Cornish heath (Erica vagans) announcing thepresence of serpentine.

At Lizard town the excursionists were met by Mr. Howard Fox,F.G.S., of Falmouth, and Mr. E. A. Wiincsh, F.G.S., of Carharrack,who had kindly undertaken to act as conductors. The party herebroke up into two groups, one under the guidance of each Director,but they practically visited the same spots. A walk through Landewednack took them to the junction of the hornblende-schist withthe serpentine, and at the Balk quarry specimens of serpentine werefreely collected. They then descended to the shore and inspectedthe granulitic, or banded crystalline series, and the gabbros of PenVoose or Perranvose. Mr. J. J. H. Teall had obligingly furnishedthe party with copies of his geological map of this district on the25-inch scale. He had also previously favoured them with thefollowing note, referring to the chief features which were likely tobe visited during the day's excursion :-

"The dominant rock at Kynance Cove is an olivine-hornblendeserpentine. Granite veins occur in the serpentine. About tht>Lizard Head several varieties of rock may be collected. A corrugated actinolitic schist is one of the most interesting. The rockshere have evidently been affected by intense mechanical forces. Onthe shore at Polpeor bosses and lenticles of greenstone (sometimesporphyritic) occur in association with green actinolitic schists. Acorrugated mica-schist is also present in considerable abundance, aswell as other rocks which it is difficult to name.

" Between Polpeor and Church Cove the cliffs are formed almostexclusively of hornblende-schist. Many varieties of this rock maybe collected, some well banded and rich in epidote, others massiveand resembling a diorite.

"North of Church cove serpt>ntine sets in, and good specimensmay be collected from the Balk quarries. At Pen Voose, north ofthe serpentine quarries, the serpentine is succeeded by the' granuliticseries' of Prof. Bonney, and on the north side of Pen Voose graniteveins, mica-diorite, gabbro, and serpentine are exposed. Transitionsfrom massive gabbro to a gabbro-schist may be here observed."

It was found desirable, through the state of the tide, to reversethis programme, but nevertheless all the chief points were visitedat some time or other in the course of the day. The last spot wasKynance Cove, which appropriately completed the Excursion as thebonne bouche of the week's work.


After a substantial meal at Kynance Cove the usual complimentary speeches were made by the President, Mr. Spratling, B.Sc.,and Mr. T. V. Holmes. The purport of these was to tender thethanks of the Association to all who had assisted in the organization of the week's Excursion, especially to tbe local leaders, withoutwbose welcome help the arrangements could never have beensuccessfully carried out.

On Saturday evening the party formally broke up, but some of themore ardent geologists, bent on unravelling, if possible, the intricacies of the Lizard rocks, remained in the district for some time andenjoyed the advantage, day after day, of visiting the principal pointsof interest under the guidance of Mr. Howard Fox and Mr. Wunsch.Ultimately they bent their way homewards, not simply laden withheavy loads of minerals and rocks, but carrying away the most pleasant recollections of their visit to the West country, while they leftbehind them a legacy of sincere gratitude for the cordiality withwhich they had been everywhere received by their Cornish friends.

REFERENCES.

Geological Survey Maps, Sheets 31, 32, 33.Ordnance Maps (New Series), Sheet 358 (Laud's End).ALLPORT, S.-" On the Metamorphic Rocks surrounding the Land's Eud

Mass of Granite," 'Quart. Journ. Geol. Soc.,' xxxii, 18'76, p. 40'7.ARGA.LL. W. H.-" On the Elvan Courses of Cornwall," 'Miners' Assoc.

Corn. and Devon for 18'75,' p. 3'7.BA.RNElT, A. K.-" Elvan Courses of Cornwall," • Miners' Assoc. Corn.,'

18'73, p. 69.BELL, R. G._u The Pliocene Beds of St. Erth," 'Trans. R. Geol. Soc.

Cornwall,' Vol. xi, 188'7. p. 45.BONNEY, REV. PRor. T. G._H On the Serpentine and Associated Rocks of

the Lizard District; with Notes by W. H. H ndleston," 'Quart. Jonrn.Geol. Soc.,' xxxiii, 18'7'7, p. 884.

-- 'The Hornblendic and other Schists of the Lizard District,' Ibid.,xxxix, 1883, p. 1.

COLLINS, J. H.-' On tbe Hensbarrow Granite District,' 18'78.-- "Tbe Goological Age of Central and West Cornwall," 'Journ. Roy.

Inst. Cornwall,' Vol. vii, 1883, p. 18. Part ii (with H. F. Collins). Vol.viii, 1884.

--- "On the Mining District of Cornwall," 'Proc. Inst. Mech. Eng.,'18'73, p. 89.

--- 'Handbook to the Mineralogy of Cornwall and Devon,' 18'71.DE LA BECHE.-' Report on the Geolol'Y of Cornwall, Devon, and West

Somerset,' 1839.FOSTER, DR. C. LE NEVE.-" On the Great Flat Lode south of Redruth

and Camborne,'" Quart. Journ. Geol. Soc.,' Vol. xxxiv, 18'78, p. 640.--- 'On some Tin Stockworks in Cornwall,' Ibid., xxxiv, 18'78, p. 654.HARRISON, W. J.-' The Geology of the Connties of England and Wales,'

1882, pp. 37 to 44.


HENWOOD, W. J._u On the Metalliferous Deposits of Cornwall," 'Trans.Roy. Gaol. Soc. Cornwall,' Vol. v, 1843.

HUNT, ROBERT.-H Treatise on British Mining," 1884.KENDALL, PERCY F., and BELL, R. G._u On the Pliocene Beds of St. Erth,"

'Qnart. Journ. Geol. Soc.,' Vol. xlii, 1886, p. 201.MAYNARD, J._u Carn Brea Hill," , Miners' Assoc. Corn.,' 1873, p. 43.MILLETT, FORTESCUE W.-" Notes on the Foraminifera of the St. Erth

Clay," 'Trans. R. Geol. Soc. Cornwall,' 1886.MOISSENICT, PROF. L.-I< Observations on the Rioh Parts of the Lodes of

Cornwall," translated by J. H. Collins, 1877.PHILLIPS, J. A._u On the Chemical Composition and Mioroscopio Constitn.

tion of oertain Cornish Rooks," 'Phil. Mag.,' Feb., 1871..--- U The Rooks of the Mining Districts of Cornwall," 'Quart. Journ.

Geol. Boc.,' xxxi, 1875, p. 319.---' On the so.caUed Greenstones of Western Cornwall,' xxxii, 1876,

p.155.--- ' A Treatise on Ore Deposits,' 1884.REID, CLEHENT.-u The Pliocene Deposits of North-Western Europe" (For

St. Erth beds). 'Nature,' xxxiv. Aug. 12, 1886, pp. 341·343.SEHHONS, W.-" The Metallio Ores of Cornwall," , Soo. Amateur GeoL,' Vol.

1, No.1, 1888.SHYTH, W. W._u On St. Miohael's Mount." 'Trans. Mining Assoo. and

lnst. of CornwaU,' Vol. i, Part iii, 1887, p. 132.SOHERVAIL, A._u On the Geologioal Struoture and Age of the Strata of

South CornwaU," 'Journ. Roy. lnst. CornwaU,' vii, 1883, p. 262.SYKONS. BRENTON.-u Treatise on the Geology of Cornwall," in 'Gazetteer

of CornwaU,' by R. Symons, Penzance, 1884.TEALL, J. J. H.-" The Metamorphosis of the Lizard Gabbros," 'Geol.

Malt.,' 1886, p. 481.--- Chapter on Serpentine in' British Petrography,' 1886, p. 104.THOKAS, JOSIAH.-u Dolcoath Main Lode," 'Miners' Assoo. Corn. and

Devon for 1883,' p. 13.USSHER, W. A. E.-' 'L'he Post-Tertiary Geololl'Y of Cornwall,' 1879.WHITLEY, NICHOLAS.- u The Effect of Geologioal Structure a.nd the Aotion

of the Wayes on the Geographioal Outline of Cornwall," 'Trans. R.Geol. Soc. Corn.,' Vol. vii, 1852, p. 220.

--- " Indioations of Glacial Action in Cornwall," 'Journ. R. lnst. Corn.waU,' No. xi, 1870, p. 184.

WOOD, SEARLES V._u On a New Deposit of Pliocene Age at St. Erth,"'Quart. Journ. Geol. Soo.,' VoL xli, 1885, p. 65.

WOODWARD, H. B.-' Geology of England and Wales,' Second Edition, 1887,pp. 75, 139, 575, 576, 579.

WORTH, R. N._U The Rocks and Minerals of CornwaU and Devon," 'Fiftyfourth Annnal Rep. of the R. Corn. Polytechnic Soo.,' 1886.

N.B.-The references given above include only a few of the more importantand recent sources of information respecting that part of CornwaUwhioh was visited by the Association. The' Transactions of the RoyalGeological Society of Cornwall,' commenced in 1818. offer a valnablerepertory of information on local geology. A list of works from theyear 1602 to 1873, inclnding the titles of 654 books, papers, maps, &0.,bearing upon the geology, mineralogy, and palreontology of Cornwall,prepared by Mr. W. Whitaker, will be found in the' Journ. Roy. Inst.Cornwall,' Vol. v, No. 16, p. 61.

Excursion to Cornwall: Monday, August 8th, to Saturday, August 13th, 1887

Documents

Transcript of Excursion to Cornwall: Monday, August 8th, to Saturday, August 13th, 1887